This invention relates to a chain conveyor for a miner and has been devised particularly though not solely for use as a transverse face conveyor.
In many types of mining operations, mining machines are provided having various types of cutter heads which cut the material to be mined, e.g. coal, from the coal face whereupon it falls to the ground beneath the cutting head. The particulate coal then requires to be collected and delivered to a central point on the miner for final delivery. The collection of coal from the face can be carried out by transverse face conveyors of the type shown in FIGS. 1 and 2 of the drawings accompanying this specification and also typically described in our co-pending Australian patent application 53776/86 corresponding to U.S. Pat.No. 4,813,530. The transverse face conveyors comprise a number of strands of chain engaged over a drive sprocket at one end of the conveyor and a parallel idler sprocket at the other end.
Chain conveyors of this type are prone to a number of problems when mining particulate materials such as coal which breaks down into material including "fine" (generally defined as coal dust and particles less than 5 mm in size) which penetrate between the links in the chain conveyor causing jamming problems due to the build up of fines within the conveyor. These problems take two major forms, firstly excessive friction on the return side of the chain due to the presence of fines under pressure between the beam which extends between the upper and lower chain runs and the lower run of chain, and secondly the phenomenon known as drive sprocket build up. In the latter phenomenon fines can build up between the chain links and the teeth in the drive sprocket causing an increase in the effective pitch circle diameter of the chain over the sprocket which either causes the chain links to jam against the adjacent gear box castings or tensions the chain to such a degree that the drive motor will jam or stall. Attempts to overcome these problems, e.g. by increasing clearance between the drive sprocket and the adjacent gear box housing or by introducing irregularities in the chain which displace and remove the fines, cause minor improvements in the situation but generally cannot overcome these problems when mining difficult materials such as coal. The coal fines sometimes behave like a hydrostatic fluid building up "head" pressure on the return run of chain between the lower skid plate of the transverse conveyor and the conveyor beam, eventually causing the drive motor to stall.